Monopropellants containing liquid fluorocarbons



United States Patent 3,164,504 MONOPROPELLANTS CONT i LIQUID FLUOROCONS William D. White, Pasadena, Doris M. Chin, Los Angeles, and John L. Jones, Pasadena, Calif., assignors to the United States of America as represented by the Secretary of the Navy No Drawing. Fiied Mar. 24, 1958, Ser. No. 723,610 6 Claims. (Cl. 149-22 (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to monopropellant fuel compositions for propulsion of underwater missiles.

Because of limited fuel storage facilities in underwater missiles it is essential that any fuel used provide a high energy output per unit weight and volume. Fuel mixtures for underwater propulsion should also have safe handling properties and good storage stability. They should possess suflicient fluidity to permit them to flow readily in small pipes and through small orifices.

Heretofore, various liquid monopropellants have been used in gas generators, rocket motors, and for underwater propulsion. Among these are hydrogen peroxide, ethylene oxide, hydrazine, nitromethane, propyl nitrate, and mixtures of various organic compounds in hydrogen peroxide solutions. The two chief disadvantages of these materials are the relatively small amount of energy which is contained in a given volume and weight of expendable and the sensitivity of most of them, this latter property making handling and utilization extremely hazardous. Further, many of them do not have sufiicient storage stability to permit storage over long periods of time without deterioration.

It is therefore an object of this invention to provide a fuel having a high energy otutput per unit weight and volume. It is a further object of this invention to provide a fuel as stated which possesses adequate fluidity and which has good storage stability.

The monopropellant fuel of this invention comprises a fluid mixture or slurry consisting of a light metal powder such as aluminum and magnesium varying in particle size from about one micron to about 300 microns suspended in a liquid fluorocarbon. The fluorocarbons used are perflourotributylamine, pertluorocyclic ether, perfluorodimethylcyclohexane, benzotrifluoride, a polymer of trifluorochloroethylene, and mixtures of these compounds.

The metal powder is present in the monopropellant fuel mixture in approximately stoichiometric ratios. This varies between 20 and 40 percent metal by weight, this being the preferred range. The fluorocarbons used must be liquid fluorocarbons. The monopropellants are made by thoroughly mixing the metal powder in the liquid fluorocarbon with conventional mixing devices. The finished product is sufliciently fluid to flow under pressure through small pipes and small orifices. This, in general, is not true of mixtures of metals with fluorocarbons.

In using the fuel it is introduced under pressure into the combustion chamber of an underwater missile in atomized form and ignited. No oxidizing agent is necessary for combustion. Sufiicient water is introduced into the combustion chamber to provide the proper reaction temperature, which is preferably around 1800 F. The heat formed from the reaction occurring in the combustion chamber is used to convert water into steam which is allowed to impinge upon the turbine blades of the propulsion machinery to drive the missile. Reaction temperatures as well as flow rates of the water, and the fuel, can be varied depending upon the fuel mixture. In contrast 3,164,504 Patented Jan. 5, 1965 to mixtures of other fluorocarbons with metals, the monopropellants of this invention possess su'fiicient fluidity to permit their passage through small diameter tubes and to permit the degree of atomization required for theircombustion.

The invention is illustrated bythe examples given in Table I below, but is not limited thereby; The magnesium used in the examples varied in particle ,size from less than one micron to that which will .pass through a 325 mesh, which is approximately 44 microns. The aluminum particles were also within this particle size range, those used preferably being of a size which will pass through a 100 mesh screen. The compositions listed in Table I were tested for explosive shock, sensitivity to direct impact, sensitivity to frictional impact and sensitivity to high temperatures, in order to determine the feasibility of handling them.

Table I.-Sh0ck and Temperature Sensitivity of Different Fuel Mixtures Percent ExpL Direct Fric- High metal Liquid shock impact tional temp.

impact 57.0 Mg N-43 d ns ns ns 66.7 Mg ga8H$C I}: 3 d* ns ns .ns 50.0 Mg 2 b ht; }d ns ns ns 55.3 Mg 0-75 (1 ns ns ns 59.4 Mg (1 ns ns 43.8 Mg Fluorolube ns snap ns 57.0 AL 43 ns ns 71.5 A1 CGHECFEI ns ns 57.8 A1- ns ns d=Detonated.

d*=Detonated, dark smoke produced initially, weak noise.

ns=Not sensitive.

N-43=Heptacosafluorotributylamine.

O75=Comp1etely fluorinated cyclic ether, CsFmO.

X-327=Perfluorodimethylcyclohexane.

Fluorolube=l olymer of trifluorochloro ethylene, SUS viscosity 0-70 at 210 F., cp. 814-49.

Standard direct impact, frictional impact and high temperature tests were used to test the above mixtures. The tests show the mixtures of magneisum and fluorocarbon derivatives can be handled safely when subjected to ordinary conditions of direct impact, frictional impact and high temperature. Mixtures of aluminum with theliquid fluorocarbons were also found to be stable to direct impact and high temperature tests. The finding that the mixtures in the above table possess suflicient insensitivity to impact, temperature changes, etc., to permit proper handling and storage is in contrast to previously held beliefs that fluorinated compounds were too explosive for use in fuels. It was found that satisfactory monopropellant fuels were produced without the addition of an oxidizing agent. The monopropellant fuels have good physical stability, this property being defined by the ability of the fuels to withstand long storage periods without sedimentation. This property, as well as the good fluidity of the monopropellants, is due to the similar densities of the components, the fluorocarbons used having been selected with this in mind. Magnesium is the preferred metal for the monopropellants, however, other light metals such as aluminum and boron may be used.

Calorimeter tests were made in a Parr Bomb Calorim eter to determine the heats ofexplosion of some monopropellant fuel mixtures. Samples of about two grams were placed in the bomb which was flushed and then pressurized with 30 atmospheres of helium. The assembled calorimeter was placed in a 25.0 C. water bath, and after thermal equilibration the sample was ignited by a hot wire delivering 5 to 7 calories of heat. The heats of explosion were then determined by standard methods. The

following equations indicate the ratio of reactants, the probable products and the measured heats of explosion:

Heat of expl.

kcal./ g. (1) 8Mg+C F 8MgF +8C 1.3 (2) 9Mg+C F O- 8MgF +MgO+8C 2.2 (3) 27Mg+2(C F N- 27MgF +24C+N 1.8

.THP-sce. .THP-sec.

D 1;. per ml.

Diesel oi1+90% H202 3. 4. 0 9 Mg+CsFw0- 8 Mg F2+MgO+8C 3. 2 5. 6 27 Mg+2(C4Fn)sN- 27 MgF +24C+Nz 4. 7 8. 2

The above energy calculations further substantiate the utility of the systems as propellants. The high energy produced from the monopropellants is due to the reaction between the fluorine and the metal. The light metals, such as magnesium, aluminum and boron have a high heat of formation with other elements.

While the utility of the monopropellants has been illustrated by their application to the propulsion of underwater missiles it is not limited to this application as they may be used for the propulsion of other type missiles 4} such as rockets, air-breathing missiles and other jetactivated devices.

It is thus seen that monopropellant fuels providing high energy per unit weight and volume, have been provided which possess sufiicient inertness for proper handling and storage and which have suflicient fluidity to flow through small orifices.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A high energy, high density monopropellant consisting essentially of from 20 to percent by weight of a metal powder from the class consisting of magnesium, aluminum and boron having a particle size ranging from about 1 micron to about 300 microns; and the remainder a liquid fluorocarbon selected from the group consisting of perfluorotributylamine, perfiuorocyclic ether, perfiuorodimethylcyclohexene, benzotrifluoride, and polytrifluorochloroethylene having a viscosity of -70 at 210 F.

2. The monopropellant of claim 1 in which the liquid fluorocarbon is perfluorotributylamine.

3. The monopropellant of claim 1 in which the liquid fluorocarbon is perfluorocyclic ether.

4. The monopropellant of claim 1 in which the liquid fluorocarbon is perfluorodimethylcyclohexane.

5. The monopropellant of claim 1 in which the liquid fluorocarbon is benzotrifluoride.

6. The monopropellant of claim 1 in which the liquid fluorocarbon is polytrifluorochloroethylene having a viscosity of 60-70 at 210 F.

No references cited.

CARL D. QUARFORTH, Primary Examiner.

LEON D. ROSDOL, Examiner. 

1. A HIGH ENERGY, HIGH DENSITY MONOPROPELLANT CONSISTING ESSENTIALLY OF FROM 20 TO 40 PERCENT BY WEIGHT OF A METAL POWDER FROM THE CLASS CONSISTING OF MAGNESIUM, ALUMINUM AND BORON HAVING A PARTICLE SIZE RANGING FROM ABOUT 1 MICRON TO ABOUT 300 MICRONS; AND THE REMAINDER A LIQUID FLUOROCARBON SELECTED FROM THE GROUP CONSISTING OF PERFLUOROTRIBUTYLAMINE, PERFLUOROCYCLIC ETHER, PERFLUORODIMETHYLCYCLOHEXENE, BENZOTRIFLUORIDE, AND POLYTRIFLUOROCHLOROETHYLENE HAVING A VISCOSITY OF 60-70 AT 210*F. 